LED has been widely used in signal indication, large screen display, and has advantages of long lifetime, good color, sturdiness, etc. At the present, only low power LED can be fabricated. The power of typical LED is only 20 mA×4V=80 mW, because the increase of the operating current will cause the rapid increase of the LED chip temperature, and in turn the luminous efficiency will decrease nearly linearly with the chip temperature increase. The efficient escape of the large quantity of heat created by LED has become the key to fabricating LED and LED lamp.
For prior typical high power LED, which is under developing as shown in FIG. 1, a LED chip 101 is bound on the light reflecting surface 102 of a metal base 103. The later is bound to a circuit board 106 by epoxy layer 111. The leads 104 and legs 105 of the LED chip 101 are connected to the electrical conduction layer 107 of the circuit board 106. An optical glue layer 108 and lens 109, 110 are provided on the chip 101. Element 110 is a fixing one.
It can be seen that LED chip is connected to a heat sink 113 via the metal base 103(heat resistance RB), epoxy layer 111(heat resistance RE), circuit board (heat resistance RP) and binding glue 112(heat resistance RA). The total resistance ΣR=RB+RE+RP+RA is great, so the chip temperature increases easily, and the luminous efficiency decreases rapidly. At the same time, the chip mounting metal base is glued to the circuit board 106. The epoxy glue is easy to be split after a long operating cycle under the condition of being cold and hot, expanded and contracted repeatedly due to the different heat expansion coefficient and different temperature increase speed between the circuit board and the metal base. Glue split increases RE, and results in LED damage by overheating. In summary, high power, high luminous efficiency and long lifetime LED for lighting is difficult for manufacturing by the prior art.